A blood-drawing device is known from DE 39 32 112 (U.S. Pat. No. 5,165,419), having an outer blood-holding receptacle that is hermetically sealed at its rear end and is sealed at its front end up to the level of a vent port, and that accommodates a concentrically positioned internal specimen tube. The specimen tube is provided on its front end with a needle that may be inserted into the vein of a patient, and at its rear end is in fluid communication with the blood-holding receptacle. The needle is fitted to a holder or Luer fitting that is fixed to a cone for the specimen tube. This blood-drawing device composed of an external blood-holding receptacle and an internal specimen tube is very bulky, and despite use of transparent material for the blood-holding receptacle and the specimen tube is not user-friendly, which complicates observation of the blood flow and makes handling cumbersome. In addition, it is difficult to take defined, small specimen quantities for analytical purposes from the large quantity of blood drawn.
After drawing venous blood, the detachable holder or Luer needle supporting the needle must first be carefully removed and disposed of. This entails the risk of needle sticks from the needle, which in addition is unavoidably wet with blood. The internal, tube- or capillary-like specimen tube is then removed in order to empty the drawn quantity of blood into the external blood-holding receptacle. Blood is likewise unavoidably drawn out when the specimen tube is removed.
Notwithstanding, this known blood-drawing device is not suitable for drawing small quantities of blood, in particular from infants and small children or small animals, on account of their other physiological considerations, in particular the much lower venous pressure. This is because the low blood pressure in these patients is not sufficient for the blood, which initially flows through the cavity of the needle, to flow opposite to the air that is invariably present in the connected specimen tube, causing the blood flow in the needle to cease. Therefore, for drawing blood from infants or the like, only the previously removed Luer needle is used, whose cavity in the insert element receives the drawn quantity of blood. Blood drawing using only the Luer fitting is very difficult and requires an experienced user. Finally, the residual quantity of blood remaining in the Luer fitting relative to the low specimen volume is excessive upon emptying into a specimen vessel, and a defined drawing of a specimen quantity is not possible at all.
The preceding similarly applies when, in particular for avoiding the residual quantity remaining in the Luer fitting, the Luer fitting is removed and then only the needle is employed. The blood specimen can then be emptied directly into a specimen vessel from the open, possibly also curved, rear end of the needle. Since it is very problematic to hold a collection vessel below the open end of the needle to enable reliable collection of the blood specimen, one person holds the patient and performs the puncture operation while another person holds the specimen vessel for receiving the blood.
To improve the drawing of venous blood in infants and is premature babies, nursing infants, and small children, it is known from DE 100 603 02 A1 to equip a hollow needle provided on its distal end with a sharpened tip, with a blood outlet, laterally angled with respect to the longitudinal axis of the hollow needle or needle, at the rear, proximal end thereof. The needle is mounted in a holder so that the grip region behind the blood outlet provides a possibility for handling or guiding. For blood drawing, a vessel that collects the flowing blood is held below the outlet opening of the needle. Compared to conventional injection needles in use, the needle for this blood-drawing device requires no special preparations such as breaking off a Luer cone. However, visual inspection of the quantity of blood to be drawn is inadequate at best, since for these blood-drawing devices of limited size the handle and/or the finger of a person drawing the blood may significantly limit or even completely obstruct the view of the outlet opening. Furthermore, as a result of the laterally angled outlet opening the needle allows optimal blood flow in only one position of use. Aside from the fact that manufacture of a curved, laterally angled needle is complex, there is also the disadvantage that the higher flow resistance in the needle as the result of the curvature hinders the flow of the blood, which in any case is drawn in only a small quantity.